Bioefficacy of Microbial Pesticides and Chemical Insecticides against Lucerne Aphid, Acyrthosiphon pisum (Harris) on Lucerne under Field Conditions

Lucerne is affected by the pea aphid, Acyrthosiphon pisum (Harris), which can reduce forage production. The study aims to evaluate the field bioefficacy of selected chemical insecticides and microbial pesticides against the lucerne aphid, Acyrthosiphon pisum (Harris), and to assess their effects on green fodder yield and treatment economics. Study design: A field experiment was laid out in a randomised complete block design (RCBD) with ten treatments and three replications. Place and Duration of Study: College Farm (Block-B), N. M. College of Agriculture, Navsari Agricultural University, Navsari, Gujarat, during Rabi 2024–25. Methodology: Lucerne variety Anand-2 was sown on 5 December 2024 at 25 cm row spacing. Treatments were applied as foliar sprays on 25 February and 12 March 2025 using a 15-litre knapsack sprayer. Aphids were counted on ten randomly selected tagged plants per net plot before spraying and at 1, 3, 5, 7, 10 and 14 days after each spray. Count data were analysed after square-root transformation and treatment means were compared using DNMRT at the 5% level. Results: Clothianidin 50 WDG at 0.005% recorded the lowest overall pooled aphid population (3.08 aphids/tiller), followed by diafenthiuron 50 WP at 0.06% (3.31 aphids/tiller) and flonicamid 50 WG at 0.015% (3.58 aphids/tiller). Clothianidin also recorded the highest green fodder yield (368 q/ha) and ICBR (1:50.36), while the water-spray control recorded the lowest yield (189 q/ha). Among microbial treatments, Lecanicillium lecanii performed better than Beauveria bassiana and Metarhizium anisopliae. Conclusion: Under the conditions of this single-location, single-season trial, clothianidin was the most effective treatment. Treatment decisions should consider current registration and label directions, pollinator exposure, non-target organisms and integrated pest management.